Ultrasound detectors are used to detect vehicles, pedestrians, or the like moving through regions such as selected portions of vehicle traffic intersections. By monitoring such movement traffic engineers can gauge changing traffic flow patterns and take appropriate action, such as adjusting the operation of traffic signal lights.
Ultrasonic energy beams projected through air by such prior art devices typically diverge considerably from the ultrasound energy source. Waveguides employed in such prior art devices commonly utilize reflective techniques and tuned assemblies to compensate for such divergence and thereby improve detection accuracy. The present invention, by contrast, shears off a cross-section of the energy pattern emitted by the ultrasound energy source and ejects it at accelerated velocity toward the target area. This enables the invention to minimize divergence by controlling the beam angle of the emitted ultrasonic energy beam.